1. Field of the Invention
This invention relates to location tracking systems for fleets of vehicles, heavy equipment or other moveable assets.
2. Related Art.
The NAVSTAR Global Positioning System (GPS), developed and implemented by the U.S. Department of Defense, uses position and time information broadcast from a constellation of up to 24 satellites, moving in non-geosynchronous orbits, to allow determination of the present time, observer location and velocity adjacent to the Earth's surface. In many different applications of use of this information, there have been systems developed for tracking vehicle position, monitoring of fleet vehicle routing and for providing navigation information to drivers. None of the previous inventions or products that are known in the art or commercially, however, provide the features of the present invention. This invention provides benefits as a low-cost inventory and asset tracking system, especially in equipment yards and asset control areas, where large inventories of vehicles and/or equipment are stored, moved and/or tracked as to their whereabouts.
In comparing the present invention to other similar position tracking systems, it should be noted that position tracking data according to the present invention are forwarded to, processed and managed at a fixed reference location site or sites, and also that the processed, corrected data are kept at the fixed location site or sites, and not transmitted back to the mobile equipment or vehicles that are being located or tracked.
By establishing this uni-directional data flow from mobile units to the fixed local units, the circuitry that is incorporated into the plurality of vehicles or assets will be simpler and lower in cost, as compared with the circuitry of the mobile equipment found within other position tracking systems known in the art. Since, according to the present invention, extra circuitry and peripheral hardware necessary for data processing and storage are comprised within a fixed location site or sites, the quantities of these more complex and expensive circuits will be far fewer than if these circuits were located within each vehicle or other asset.
In U.S. Pat. No. 6,611,755 B1 to Coffee et al., a vehicle fleet management system is described, which has application in tracking the activities of slurry, aggregate and ready-mix concrete trucks.
In U.S. Pat. No. 6,453,237 B1 to Fuchs et al., describes an apparatus and method is described by which vehicle position is determined based upon receipt at the vehicle of GPS satellite signals and receipt of the differential correction data provided by fixed location devices. Similar to Coffee et al. above, this invention relies upon receiving and processing of information at each vehicle, requiring more complex and expensive circuitry.
In U.S. Pat. No. 6,700,533 to Werb et al. is described a system which requires that the fixed local devices be accurately geo-positioned prior to use and capable of making differential GPS corrections.